Progressive fork springs and spacers

Seriously considering the progressive fork springs for my gpz550. The only thing that's confusing me is that on the progressive website it states "You must add a spacer (length indicated) (19) to spacer furnished with springs or make a spacer that is the same length as the two combined."


So it seems I have to install another spacer to correctly adjust preload. How to do calculate how long of a spacer to use to adjust preload? I really need feedback from anyone here who has installed these springs; it doesn't need to be the same model as mine. I know how to change the springs, but have no idea what length of a spacer I need. What does a "19" spacer mean since that's what the website recommended?

Quick guess but it probably means the length in mm's

Redox, Perhaps this will help. Pre-load spacers do just as name implys, they put "some tension" on the fork springs when forks are assembled and at full extension.the amount of said "tension/(pre-load)is a "tuning variable" which is determined by, length, & strengh (rate) of springs, weight of bike & rider, available amount of travel of fork & weight distribution (fore & aft). for our period conventional forks an inch to "1 1/2" pre-load ( the difference from spacer top at rest(fork iextended) to seated position w /cap installed, is as good as any to start. (assuming @ 6-8 inches front travel & @ 4" rear. what you're looking for is "optimum sag distance" or the distance from "full extension" to where tubes reside in loweres w/ bike at rest(centered) & rider in place. ( I like @ 3/4 to 1" sag tho I'm a light weight (150 lbs) & like a relitevly soft ride. Pcv tubing is cheep, easy to cut & works well for spacer material. a zip tie around fork tube (just above "wiper") is an easy indicator of typical travel whilst riding. optimum sag, is where roughly 80% of the total travel available is used w/ "spirited" riding. (leaving 20% "cush" factor for R/R tracks Potholes etc). Please note, these are all just "rough estimates" & your needs may vary. Once "ride heights" front & rear are "ball park" damping rates can be addressed. fork oil weight,amounts drilling dampers & "emulators" are all options. I've heard it said. "you can't make chicken salad out of chicken shit", and will agree that while you may not be able to equal the "tuneability/acuaracy" of modern suspensions, there's a lot to be "ganed" by "tuning" these old units...G

I just sold the set I had for that bike for $65. brand new still in the box. The kit comes with everything you need. kit #11-1111

The fork tubes and caps have very fine threads.

The soft aluminum threads on the caps are easily damaged or stripped if cross threaded, which may occur when attempting to start threading the caps into position into tops of fork tubes.

When assembling threaded parts together, we are all familiar with the tactile "feel" usually sensed to initially notice either proper meshing or improper cross-threading.

Overcoming the fork spring "pre-load" reduces the tactile feel, thereby requiring extra care be taken not to cross-thread the caps.

As a practical matter, "some" pre-load is needed to prevent the spring from clanking back and forth inside the tube.

The "optimum" pre-load varies with rider desires for the particular bike.

Good Fortune!

Another popular thing guys do on here is run Race Tech Cartridge Emulators: racetech.com/html_files/EMULATORGV.HTML

The kit comes with spring spacers cut to the correct length. I believe they are about 1.75" It is no harder to install the caps than if the spacers are not there.

otakar wrote: The kit comes with spring spacers cut to the correct length. I believe they are about 1.75" It is no harder to install the caps than if the spacers are not there.

Yes, the cap should easily start threading where it doesn't encounter spring tension until after threading begins.

On Z1 and KZ900 with stock fork springs replaced by "Progressive" springs and spacers provided by Progressive for the respective models, the cap encounters spring tension before it starts threading into the forks (this being at maximum fork extension). But, I don't recall whether this occurred using a stock spring within its free length service limit.

Good Fortune!

The springs should always extend between 1"-2" past the top of the tube at free length with tube fully extended. This is what is called pre-load.

So Otakar, you're saying if I order pn #11-1111, I won't need anything else? Just drop and go? I will probably get the mechanic to drop them in when he changes the fork oil.

In regards to my forks, I do not have a threaded cap. It's a cap that's held down by an internal circlip. You have to compress the cap to remove the circlip, then remove the cap and spring.


mtbspeedfreak, I assume you need to measure your fork diameter and what not to find the correct type of racing emulator? Is it a better choice than the springs?

To be perfectly honest- I don't know what exactly you need as I have not performed either modification. Although I'm intently watching this thread. I'm leaning towards the emulator route though, but that'll be performed after I get aftermarket dual front discs.